title: Characterization of metabolites of GLS4 in humans using ultrahigh-performance liquid chromatography/quadrupole time-of-flight mass spectrometry.
abstract: BACKGROUND
  GLS4 is a heteroaryldihydropyrimidine compound that inhibits hepatitis B virus (HBV) replication by drug-induced depletion of nucleocapsids. It is currently undergoing clinical trials in China to treat HBV infection. The aim of this study was to identify the metabolites of GLS4 in humans.
  
  
  METHODS
  A rapid and sensitive method based on ultrahigh-performance liquid chromatography/quadrupole time-of-flight tandem mass spectrometry was used to identify GLS4 metabolites in human plasma, urine, and feces after an oral dose of 120 mg GLS4.
  
  
  RESULTS
  A total of 27 metabolites were detected and identified by comparing the accurate molecular masses, retention times and spectral patterns of the analytes with those of the parent drug. Nine metabolites were confirmed by comparison with reference substances. All of the metabolites had a bromine atom and displayed the isotope ion of [M + H](+)/[M + H + 2](+) at a ratio of 1:1. Fragmentation of the dihydropyrimidine structure was characterized by the loss of the m-bromofluorobenzene group to generate an ion at m/z 220.0175. The morpholine ring was characterized by an ion at m/z 100.0757.
  
  
  CONCLUSIONS
  The metabolites of GLS4 in humans were identified by the diagnostic ions of dihydropyrimidine and morpholine rings. GLS4 underwent extensive dealkylation, hydrolysis, dehydrogenation, oxidation, and glucuronidation reactions in humans.
authors.affiliation: Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 501 Haike Road, Shanghai, 201203, P.R. China.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhou
authors.forename: Liang
authors.initials: L
authors.lastname: Li
authors.forename: Pan
authors.initials: P
authors.lastname: Deng
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Chen
authors.forename: Dafang
authors.initials: D
authors.lastname: Zhong
mesh_terms: D000998:Antiviral Agents / Q000737:chemistry / Q000378:metabolism* / Q000493:pharmacokinetics*; D002851:Chromatography, High Pressure Liquid; D006509:Hepatitis B / Q000188:drug therapy*; D006801:Humans; D008297:Male; D013058:Mass Spectrometry; D011743:Pyrimidines / Q000737:chemistry / Q000378:metabolism* / Q000493:pharmacokinetics*; D013844:Thiazoles / Q000737:chemistry / Q000378:metabolism* / Q000493:pharmacokinetics*
chemical_list: D000998:Antiviral Agents; D011743:Pyrimidines; D013844:Thiazoles; C588160:ethyl 4-(2-bromo-4-fluorophenyl)-6-(morpholinomethyl)-2-(2-thiazolyl)-1,4-dihydropyrimidine-5-carboxylate